<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .background_color1{
            width:100px;
            height:50px;
            background-color:red;
        }
        .background_color2{
            background-color: black;
            width:100px;
            height:50px;
        }
        .background_color3{
            width:100px;
            height:50px;
            background-color: blue;
        }
        #pink{
            color:blue;
        };
        .font-size-box{
            
        }
    </style>
</head>
<body>
    <h4 id="pink">box</h4>
    <div class="background_color1">box1</div>
    <div class="background_color2"></div>
    <div class="background_color3"></div>
</body>
</html>